The present invention relates to a packet transmission system for the voice signal information.
In a recent packet switched network, for example the inter-net, request of real-time voice communication is an important subject to attain. The real-time voice communication treats encoded voice signal as packetized information for transmitting a network.
Depend on a network condition, delays of voice packets may happen. In that cases, receiving side copes with the delays by inserting complement voice packets instead of the delay packets, for operating voice decoder.
Therefore, The voice communication has some delays, so it will need to discard some receiving packets for recovering the delays.
The present, the discarding is performed without consideration about characters of receiving packets. Hence, it has a possibility that quality of synthetic voice signal is deteriorated.
It is an object of the invention to provide an improved voice packet decoder for network voice communication which can recover packet delays without deteriorating of a synthetic voice signal quality.
To solve such a problem, a voice packet decoder of the present invention has following operations. A receiving buffer stores a plurality of receiving packets given from a network and outputs the oldest packet in every fixed period as an encoded packet. When in every the fixed period, if the receiving buffer stores no packets, then a complement packet insert circuit inserts a predetermined complement packet and a counter adds one. Furthermore, a voice decoder generates a synthetic voice signal based on the encoded packet. A speech/non-speech detection circuit detects whether the synthetic voice signal is speech signal or non-speech signal. When a result of the speech/non-speech detecting is non-speech, the counter""s value is more than zero, and a number of the receiving packets in the receiving buffer stored is more than one, then a receiving buffer controller discards the oldest packet stored in the receiving buffer and subtracts one from the counter""s value.